master 7778f83b3e 2/3: Use struct for saved strings in the reader

[Mattias Engdegård]

branch: master
commit 7778f83b3e691716522b30393d33ae20cba9a2b0
Author: Mattias Engdegård <mattiase@acm.org>
Commit: Mattias Engdegård <mattiase@acm.org>

    Use struct for saved strings in the reader
    
    * src/lread.c (saved_doc_string, saved_doc_string_size)
    (saved_doc_string_length, saved_doc_string_position)
    (prev_saved_doc_string, prev_saved_doc_string_size)
    (prev_saved_doc_string_length, prev_saved_doc_string_position):
    Replace with...
    (struct saved_string, saved_strings): ...this.
    * src/lread.c (Fload, skip_lazy_string, get_lazy_string):
    Adapt code.
---
 src/lread.c | 157 ++++++++++++++++++++++++------------------------------------
 1 file changed, 62 insertions(+), 95 deletions(-)

diff --git a/src/lread.c b/src/lread.c
index 58fe3c5a9c..d16df32ca3 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -131,25 +131,15 @@ static ptrdiff_t read_from_string_limit;
 /* Position in object from which characters are being read by `readchar'.  */
 static EMACS_INT readchar_offset;
 
-/* This contains the last string skipped with #@.  */
-static char *saved_doc_string;
-/* Length of buffer allocated in saved_doc_string.  */
-static ptrdiff_t saved_doc_string_size;
-/* Length of actual data in saved_doc_string.  */
-static ptrdiff_t saved_doc_string_length;
-/* This is the file position that string came from.  */
-static file_offset saved_doc_string_position;
-
-/* This contains the previous string skipped with #@.
-   We copy it from saved_doc_string when a new string
-   is put in saved_doc_string.  */
-static char *prev_saved_doc_string;
-/* Length of buffer allocated in prev_saved_doc_string.  */
-static ptrdiff_t prev_saved_doc_string_size;
-/* Length of actual data in prev_saved_doc_string.  */
-static ptrdiff_t prev_saved_doc_string_length;
-/* This is the file position that string came from.  */
-static file_offset prev_saved_doc_string_position;
+struct saved_string {
+  char *string;                        /* string in allocated buffer */
+  ptrdiff_t size;              /* allocated size of buffer */
+  ptrdiff_t length;            /* length of string in buffer */
+  file_offset position;                /* position in file the string came 
from */
+};
+
+/* The last two strings skipped with #@ (most recent first).  */
+static struct saved_string saved_strings[2];
 
 /* A list of file names for files being loaded in Fload.  Used to
    check for recursive loads.  */
@@ -1605,13 +1595,12 @@ Return t if the file exists and loads successfully.  */)
   if (!NILP (Ffboundp (Qdo_after_load_evaluation)))
     call1 (Qdo_after_load_evaluation, hist_file_name) ;
 
-  xfree (saved_doc_string);
-  saved_doc_string = 0;
-  saved_doc_string_size = 0;
-
-  xfree (prev_saved_doc_string);
-  prev_saved_doc_string = 0;
-  prev_saved_doc_string_size = 0;
+  for (int i = 0; i < ARRAYELTS (saved_strings); i++)
+    {
+      xfree (saved_strings[i].string);
+      saved_strings[i].string = NULL;
+      saved_strings[i].size = 0;
+    }
 
   if (!noninteractive && (NILP (nomessage) || force_load_messages))
     {
@@ -3445,64 +3434,52 @@ skip_lazy_string (Lisp_Object readcharfun)
         record the last string that we skipped,
         and record where in the file it comes from.  */
 
-      /* But first exchange saved_doc_string
-        with prev_saved_doc_string, so we save two strings.  */
-      {
-       char *temp = saved_doc_string;
-       ptrdiff_t temp_size = saved_doc_string_size;
-       file_offset temp_pos = saved_doc_string_position;
-       ptrdiff_t temp_len = saved_doc_string_length;
-
-       saved_doc_string = prev_saved_doc_string;
-       saved_doc_string_size = prev_saved_doc_string_size;
-       saved_doc_string_position = prev_saved_doc_string_position;
-       saved_doc_string_length = prev_saved_doc_string_length;
-
-       prev_saved_doc_string = temp;
-       prev_saved_doc_string_size = temp_size;
-       prev_saved_doc_string_position = temp_pos;
-       prev_saved_doc_string_length = temp_len;
-      }
+      /* First exchange the two saved_strings.  */
+      verify (ARRAYELTS (saved_strings) == 2);
+      struct saved_string t = saved_strings[0];
+      saved_strings[0] = saved_strings[1];
+      saved_strings[1] = t;
 
       enum { extra = 100 };
-      if (saved_doc_string_size == 0)
+      struct saved_string *ss = &saved_strings[0];
+      if (ss->size == 0)
        {
-         saved_doc_string = xmalloc (nskip + extra);
-         saved_doc_string_size = nskip + extra;
+         ss->size = nskip + extra;
+         ss->string = xmalloc (ss->size);
        }
-      if (nskip > saved_doc_string_size)
+      else if (nskip > ss->size)
        {
-         saved_doc_string = xrealloc (saved_doc_string, nskip + extra);
-         saved_doc_string_size = nskip + extra;
+         ss->size = nskip + extra;
+         ss->string = xrealloc (ss->string, ss->size);
        }
 
       FILE *instream = infile->stream;
-      saved_doc_string_position = (file_tell (instream) - infile->lookahead);
+      ss->position = (file_tell (instream) - infile->lookahead);
 
-      /* Copy that many bytes into saved_doc_string.  */
+      /* Copy that many bytes into the saved string.  */
       ptrdiff_t i = 0;
       int c = 0;
       for (int n = min (nskip, infile->lookahead); n > 0; n--)
-       saved_doc_string[i++] = c = infile->buf[--infile->lookahead];
+       ss->string[i++] = c = infile->buf[--infile->lookahead];
       block_input ();
       for (; i < nskip && c >= 0; i++)
-       saved_doc_string[i] = c = getc (instream);
+       ss->string[i] = c = getc (instream);
       unblock_input ();
 
-      saved_doc_string_length = i;
+      ss->length = i;
     }
   else
     /* Skip that many bytes.  */
     skip_dyn_bytes (readcharfun, nskip);
 }
 
+/* Given a lazy-loaded string designator VAL, return the actual string.
+   VAL is (FILENAME . POS).  */
 static Lisp_Object
 get_lazy_string (Lisp_Object val)
 {
-  char *saved = NULL;
-  file_offset saved_position;
   /* Get a doc string from the file we are loading.
-     If it's in saved_doc_string, get it from there.
+     If it's in a saved string, get it from there.
 
      Here, we don't know if the string is a bytecode string or a doc
      string.  As a bytecode string must be unibyte, we always return a
@@ -3511,47 +3488,37 @@ get_lazy_string (Lisp_Object val)
 
   /* Position is negative for user variables.  */
   EMACS_INT pos = eabs (XFIXNUM (XCDR (val)));
-  if (pos >= saved_doc_string_position
-      && pos < (saved_doc_string_position + saved_doc_string_length))
-    {
-      saved = saved_doc_string;
-      saved_position = saved_doc_string_position;
-    }
-  /* Look in prev_saved_doc_string the same way.  */
-  else if (pos >= prev_saved_doc_string_position
-          && pos < (prev_saved_doc_string_position
-                    + prev_saved_doc_string_length))
-    {
-      saved = prev_saved_doc_string;
-      saved_position = prev_saved_doc_string_position;
-    }
-  if (saved)
-    {
-      ptrdiff_t start = pos - saved_position;
-      ptrdiff_t from = start;
-      ptrdiff_t to = start;
+  struct saved_string *ss = &saved_strings[0];
+  struct saved_string *ssend = ss + ARRAYELTS (saved_strings);
+  while (ss < ssend
+        && !(pos >= ss->position && pos < ss->position + ss->length))
+    ss++;
+  if (ss >= ssend)
+    return get_doc_string (val, 1, 0);
+
+  ptrdiff_t start = pos - ss->position;
+  char *str = ss->string;
+  ptrdiff_t from = start;
+  ptrdiff_t to = start;
 
-      /* Process quoting with ^A, and find the end of the string,
-        which is marked with ^_ (037).  */
-      while (saved[from] != 037)
+  /* Process quoting with ^A, and find the end of the string,
+     which is marked with ^_ (037).  */
+  while (str[from] != 037)
+    {
+      int c = str[from++];
+      if (c == 1)
        {
-         int c = saved[from++];
-         if (c == 1)
-           {
-             c = saved[from++];
-             saved[to++] = (c == 1 ? c
-                            : c == '0' ? 0
-                            : c == '_' ? 037
-                            : c);
-           }
-         else
-           saved[to++] = c;
+         c = str[from++];
+         str[to++] = (c == 1 ? c
+                      : c == '0' ? 0
+                      : c == '_' ? 037
+                      : c);
        }
-
-      return make_unibyte_string (saved + start, to - start);
+      else
+       str[to++] = c;
     }
-  else
-    return get_doc_string (val, 1, 0);
+
+  return make_unibyte_string (str + start, to - start);
 }